Alberta's Driver's Guide says "in urban areas, U-turns are not permitted on a roadway between intersections and at an alley intersection". What would be the reason or reasons behind the prohibitions? If I have asked the question on the wrong forum, please let me know. Thank you!

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    I think this is probably off-topic; this SE site is for "what is the law", not "why is the law like this?" - the latter is more about politics, but you might get a better answering in Motoring in this specific case. The obvious answers are "improving road safety" and "improving traffic flow" - neither of which are legal questions. Apr 26, 2023 at 7:45
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    I’m voting to close this question because reasoning for law is in general off topic but for some fringe cases where the interaction of other laws leads to strange outcomes.
    – Trish
    Apr 26, 2023 at 8:19

1 Answer 1


The most likely reason is that in the Americas, most cities are built in grids. For the first couple of hundred years of European colonization, grid cities were highly efficient, as it was easy to survey and parcel off property and allowed for movement of pedestrian and equine traffic efficiently in lines (go two blocks up and two blocks right, and you're there). Then, everything changed when the automobile was invented... Most roads were not built with the car in mind and they were a bit faster and less mobile for grid cities. This lead to a situation where many roads in urban cores are more crowded because of cars, but the roads cannot be expanded because the property along them is owned by many different parties, and that's not with historical structures that are protected from being torn down.

As such, it may be prudent to add stricter controls to the vehicle flow in cities by limiting the ability to turn around. One of the main disadvantages of grids for automobiles is that there is frequent intersections, which disrupts the flow of traffic because often only one direction can go. Often to ease this, "Right on Red" rules are introduced that allow traffic making right hand turns to do so after stopping for oncoming traffic. This helps reduce the wait for the green light and allows more people to continue on their journey and free up space on that section of a road. Because a U-turn is a wide turn on a left hand turn, it might risk the people who have Right on Red (often times if traffic is only allowed to make left hand turns on a green left hand arrow, the right hand turns are also given a green arrow). U-Turns there for are difficult for Right on Red traffic to predict because there is no way to indicate if a car is making a left or a U. Furthermore, in a grid city, a U-Turn can be achieved by making three lefts and then a right hand turn onto the original road, so it's not much of an inconvenience.

This is likely a quirk of Alberta, as the U.S. (where driving rules tend to be similar.) U-turns are typically permitted unless signs specifically disallow it. We do have occasional intersections where signs will indicate a lane can make a U-Turn (these generally have two dedicated left hand turn lanes, with the furthest left turn being a U-turn permitted lane, and all other left turn only lanes not permitting it.).

  • Thank you so very much for your detailed explanations!
    – Maurice
    Apr 26, 2023 at 16:26
  • @Maurice No problem. I wouldn't say this is a definitive answer, but most traffic laws are done to promote traffic flow while avoiding dangerous road conditions. U-Turns tend to be one of the riskier turns possible, even if they are permitted.
    – hszmv
    Apr 26, 2023 at 16:38
  • FYI In Ontario, there is no such thing as a U-turn. There is instead a"turn to reverse direction" The sign prohibiting these turns has an inverted U, with an arrow on the left hand end. ontario.ca/document/official-mto-drivers-handbook/… A three point turn is prohibited where such a sign is displayed thestar.com/news/gta/2017/09/12/…
    – DJohnM
    Apr 27, 2023 at 22:11
  • @DJohnM A U-Turn is represented by the inverted U sign. It's a left hand turn (typically at an intersection that results in the vehicle going in the opposite direction of it's original direction on the same road. The three point turn is also known as a K-turn.
    – hszmv
    Apr 28, 2023 at 10:54

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